Question

A rock is dropped from rest from a bridge and strikes the water in 5.0 sec. How high is the bridge? Write the distance as a positive number.

A) 122.5 m
B) 49 m
C) 122.5 ft
D) 245 m

Answer 1

Using the equation of motion for an object under gravity, the bridge's height is determined to be 122.5 meters when a rock is dropped and strikes the water in 5.0 seconds.

Step-by-step explanation:

To determine how high the bridge is from which a rock is dropped and strikes the water in 5.0 seconds, we can use the equation of motion under the influence of gravity:

s = ut + ½ at²

Where:

s = Displacement (the height of the bridge, which we are looking to find)

u = Initial velocity (since the rock is dropped from rest, u = 0)

t = Time (5.0 seconds)

a = Acceleration due to gravity (9.8 m/s² on Earth)

So the equation becomes:

s = 0 x 5.0 + ½ x 9.8 m/s² x (5.0 s)²

Calculating this we get:

s = 0.5 x 9.8 x 25

s = 4.9 x 25

s = 122.5 meters

Therefore, the bridge is 122.5 meters high. The correct answer is A) 122.5 m. Remember, distance is considered a positive number when solving physics problems related to displacement and height.